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排序方式: 共有120条查询结果,搜索用时 148 毫秒
101.
Coe JW Bianco KE Boscoe BP Brooks PR Cox ED Vetelino MG 《The Journal of organic chemistry》2003,68(26):9964-9970
Oxidative ring closure of alkyl-substituted 2-hydroxyacetophenone trifluoromethanesulfonate esters (triflates) occurs upon exposure to base in anaerobic DMF at 20-90 degrees C. Alkyl substitution is required for ring closure. A migrated enol triflate product forms at lower temperature in high yield via migration of the trifluoromethanesulfonate in the unsubstituted and monoalkyl-substituted cases. The alkyl-substituted enol triflates also enter into the benzofuran-3-one ring-forming process under thermal cyclization conditions. Potential mechanistic pathways are evaluated. 相似文献
102.
103.
104.
Benjamin J. Coe James A. Harris Simon J. Coles Michael B. Hursthouse 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(7):857-858
In the title compound, C15H18N3+·C7H7O3S?, the phenylene and pyridyl rings are somewhat twisted with respect to each other, forming a dihedral angle of 23.49 (6)°. The compound contains a dipolar chromophoric cation, but crystallizes in the centrosymmetric space group P21/n and is thus not expected to display quadratic non‐linear optical effects. 相似文献
105.
Benjamin J. Coe James A. Harris Thomas Gelbrich Michael B. Hursthouse 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):1487-1489
The crystal structure of the dipolar chromophoric title compound, C20H20N3+·PF6?, is described. The phenylene and pyridyl rings are almost coplanar [dihedral angle 7.5 (2)°], but the phenyl substituent forms a dihedral angle of 56.6 (1)° with the pyridyl ring. The compound crystallizes in the non‐centrosymmetric space group Cc and is a likely candidate for the display of quadratic non‐linear optical effects. 相似文献
106.
Dr. Samuel D. L. Holman Alfie G. Wills Dr. Neal J. Fazakerley Dr. Darren L. Poole Dr. Diane M. Coe Dr. Leonard A. Berlouis Dr. Marc Reid 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(13):e202103728
An electrochemical method for the green and practical synthesis of a broad range of substituted isoxazoline cores is presented. Both aryl and more challenging alkyl aldoximes are converted to the desired isoxazoline in an electrochemically enabled regio- and diastereoselective reaction with electron-deficient alkenes. Additionally, in-situ reaction monitoring methods compatible with electrochemistry equipment have been developed in order to probe the reaction pathway. Supporting analyses from kinetic (time-course) modelling and density functional theory support a stepwise, radical-mediated mechanism, and discounts hypothesised involvement of closed shell [3+2] cycloaddition pathways. 相似文献
107.
Paul L. Coe 《Journal of fluorine chemistry》1999,100(1-2):45-52
The use of polyfluorovinyl lithium reagents in synthesis since their original discovery almost simultaneously by Seyferth and Tarrant and their development by Normant is reviewed. More recent developments in the field using CFC replacements as starting materials has given a new impetus to the use of these important reagents as building blocks for the development of new materials. These new reactions are also reviewed. 相似文献
108.
Boubekeur-Lecaque L Coe BJ Harris JA Helliwell M Asselberghs I Clays K Foerier S Verbiest T 《Inorganic chemistry》2011,50(24):12886-12899
Nine nonlinear optical (NLO) chromophores with pyridinium electron acceptors have been synthesized by complexing new proligands with {Ru(II)(NH(3))(5)}(2+) electron-donor centers. The presence of long alkyl/fluoroalkyl chain substituents imparts amphiphilic properties, and these cationic complexes have been characterized as their PF(6)(-) salts by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. Each complex shows three reversible/quasireversible redox processes; a Ru(III/II) oxidation and two ligand-based reductions. The energies of the intense visible d → π* metal-to-ligand charge-transfer (MLCT) absorptions correlate to some extent with the ligand reduction potentials. (1)H NMR spectroscopy also provides insights into the relative electron-withdrawing strengths of the new ligands. Single crystal X-ray structures have been determined for two of the proligand salts and one complex salt, [Ru(II)(NH(3))(5)(4-C(16)H(33)PhQ(+))]Cl(3)·3.25H(2)O (PhQ(+) = N-phenyl-4,4'-bipyridinium), showing centrosymmetric packing structures in each case. The PF(6)(-) analogue of the latter complex has been used to deposit reproducibly high-quality, multilayered Langmuir-Blodgett (LB) thin films. These films show a strong second harmonic generation (SHG) response from a 1064 nm laser; their MLCT absorbance increases linearly with the number of layers (N) and I(2ω)/I(ω)(2) (I(2ω) = intensity at 532 nm; I(ω) = intensity at 1064 nm) scales quadratically with N, consistent with homogeneous deposition. LB films on indium tin oxide (ITO)-coated glass show electrochemically induced switching of the SHG response, with a decrease in activity of about 50% on Ru(II) → Ru(III) oxidation. This effect is reversible, but reproducible over only a few cycles before the signal from the Ru(II) species diminishes. This work extrapolates our original solution studies (Coe, B. J. et al. Angew. Chem., Int. Ed.1999, 38, 366) to the first demonstration of redox-switching of NLO activity in a molecular material. 相似文献
109.
EI Balmond DM Coe MC Galan EM McGarrigle 《Angewandte Chemie (International ed. in English)》2012,51(36):9152-9155
Alpha rules: A thiourea acts as an efficient organocatalyst for the glycosylation of protected galactals to form oligosaccharides containing a 2-deoxymonosaccharide moiety. The reaction is highly stereoselective for α-linkages and proceeds by way of a syn-addition mechanism. 相似文献
110.
The photoelectron spectra of (H2O)(n = 2-69) - and (D2O)(n = 2-23) - are presented, and their spectral line shapes are analyzed in detail. This analysis revealed the presence of three different groupings of species, each of which are seen over the range, n = 11-16. These three groups are designated as dipole boundlike states, seen from n = 2-16, intermediate states, found from n = 6-16, and bulk embryonts, starting at n = 11 and continuing up through the largest sizes studied. Almost two decades ago [J. V. Coe et al., J. Chem. Phys. 92, 3980 (1990)], before the present comprehensive analysis, we concluded that the latter category of species were embryonic hydrated electrons with internalizing excess electrons (thus the term embryonts). Recent experiments with colder expansion (high stagnation chamber pressures) conditions by Neumark and coworkers [J. R. R. Verlet et al., Science 307, 93 (2005)] have also found three groups of isomers including the long-sought-after surface states of large water cluster anions. This work confirms that the species here designated as embryonts are in the process of internalizing the excess electron states as the cluster size increases (for n > or = 11). 相似文献